Use SDK Constant for NeighboringCellInfo Docstring

As per API council feedback, when documenting
SDK-level-specific behavior and recommendations, the
document should use and link to the SDK constant rather
than its value. Update the docstring accordingly, and
also some minor verbiage tweaks.

Bug: 117154674
Test: compilation; docstring-only change
Change-Id: I0ee56a4d76a311a8e0136766ef45aeda46cd12b4